1. Field of the Invention
The invention generally relates to rotary driven cylindrical cutters and scarifiers for use in earth-working, mining, or other in situ disintegration of hard materials. The invention is particularly directed to such rotary driven cylindrical cutters and scarifiers as incorporate means for feeding or excavating the material cut or mined away from its initial location generally to a second material carrier.
2. Background of the Invention
In general, roadway mining or planing equipment includes a rotary driven cylindrical comminuting drum which acts to scarify and to mine the top portion of the asphaltic road surface in situ. The rotary driven drum includes flighting on the drum which acts to collect and move the mined material toward the center of the drum where it can be removed. Often the mined material is then remixed with additional bituminous material and thereafter re-deposited as a newly formed smooth asphaltic surface.
In some prior art devices of this type, the flighting is itself formed from a plurality of cutting bit support members which are connected to the curved surface of the cutting drum by bolts which pass from the upper surface of the flighting downward into the drum to engage threaded openings in the drum. Alternatively, the bolts may pass through the surface of the drum to engage lock washers and threaded nuts on the interior of the drum. A plurality of the cutting bit supporting members can be arranged end-to-end so as to form a substantially continuous helical flighting. The top surface of the helical flighting is elevated above the curved surface of the drum. The top surface includes angled openings into which conventional cutting bits are received.
In use, the abrasive forces, which often include rather high value sudden shocks, are transmitted from the cutting bits into the supporting members and the bolts securing the supporting members to the smooth drum surface. The forces occasionally become large enough to shear the securing bolts, causing the machine to be stopped often for considerable lengths of time. The repair and replacement of the cutting bit supporting member damaged in this manner typically necessitates the use of an easy-out or similar removing tool in the field to remove the portions of the sheared bolts remaining in the drum. This is a time-consuming repair job which results in considerable expense to the road-mining machine operator.
In an attempt to avoid the problems presented by the bolt-secured supporting members, other roadway planing devices include a continuous flighting welded in place in helical fashion on the surface of the drum. A plurality of individual cutting bit support blocks are welded to the upper edge of the flighting. The support block includes a recess for receiving a cutting bit of a chisel cutter preferably having a tungsten carbide tip or the like.
In use, the cutting bits vibrate and otherwise move within the support block recess. Particularly in the presence of abrasive dust from the roadway mining operation, the vibration and movement of the cutting bits act to enlarge the recesses to such an extent that the cutting bit is no longer retained. It then becomes necessary to remove the old support block, usually with the aid of a cutting torch, and to weld a new support block in its place. Again, this repair job is difficult to do in the field and still achieve accurate alignment of the support block on the flighting section. Misalignment of the support block results in undesirable lateral forces on a new cutting bit which in turn results in very fast wear and ultimate failure of the replaced parts.
One solution for the above described problems is disclosed in U.S. patent application Ser. No. 10/705,709, filed Nov. 11, 2004, published May 12, 2005 (US 2005/0098015 A1), and entitled “Angular Tool And Holding Block”, which is assigned to the assignee of the present application and is hereby incorporated by reference herein. The angular tool and holding block described in this published patent application provides a tool holder, a cutting bit, and a retainer for maintaining the tool holder at a prescribed position relative to the holding block. The tool holder includes a generally rectangular body portion, which can be square, dimensioned so that the tool holder body can be at least partially received in a slot formed in the holding block at a fixed orientation.
The tool holder also has a lower planar tapered portion-that is obliquely inclined to face laterally and upwardly. The lower planar tapered portion of the tool holder can be upwardly inclined at an angle of between about 1 degree and 5 degrees, and laterally inclined at an angle of between about 5 degrees and 15 degrees. The retainer includes a planar tapered surface inclined with respect to the line of action that intersects the perimeter surface. The planar tapered surface of the retainer can be inclined at an angle about equal to the lateral angle of inclination of the lower planar tapered portion of the tool holder. As the retainer is inserted into the opening, the planar tapered surface of the retainer contacts the lower planar tapered portion of the tool holder so that a downward and laterally inward force can be applied to the tool holder by the retainer to maintain the tool holder in the tool holder slot of the holding block.
This solution, however, requires a specially formed tool holder having a lower planar tapered portion. Therefore, standard rectangular or square tool holders cannot be used. Thus, there remains a need for a holder and holding block that retains the cutting bit at a prescribed position during any mining, cutting or other similar operation, which also enables quick replacement of the cutting bit or tool holder at the same location with a minimum of effort and time, and is capable of utilizing standard rectangular or square shaped tool holders.